The objective of this investigation is to provide new information on the regulation of acetylcholine synthesis in the central nervous system. While there are a variety of studies that suggest that the synthesis of acetylcholine is regulated by feedback inhibition, there have been various criticisms of these studies. Studies utilizing drugs which increase the level of acetylcholine in brain tissue have shown a decrease in synthesis of acetylcholine by this tissue. However, the effect on synthesis could result from an effect of the drug other than its elevation of acetycholine levels. Further the use of whole brain tissue is in these studies may not reflect accurately the processes that occur at the nerve terminal. I propose to use an anatomically defined cholinergic system, separate the cholinergic nerve endings from the cell bodies and pre- subably its input, and then examine acetylcholine synthesis in these nerve endings where there is presumably no more release. The system that I will utilize is the septal-hippocampal cholinergic projection. By placing a lesion in the septum, it is possible to remove most of the cholinergic neurons in the hippocampus after long intervals. At short time intervals after placement of lesion, acetylcholine levels rise dramatically in the hippocampus. This latter finding is consistent with the view that release of acetylcholine from nerve endings ceases when the cell bodies are destroyed. I propose to examine acetylcholine synthesis in slices of hippocampus from animals acutely lesioned in the septum. The plan would be to place radio frequency lesions in the septum of rats, remove the hippocampus from their brains after one to ten hours and study the synthesis of acetylcholine in these hippocampal tissues and compare it with that of tissue from sham-lesioned Animals. Two methods will be utilized to study the synthesis of acetylcholine. The first method involves the incubation of brain tissue with radioactive glucose. This method will show the incorporation of labeled acetate into the acetylcholine molecule. The second method, which will examine the the incorporation of choline into acetylcholine, involves the incubation of tissue with low concentrations of radioactive choline.